ProjectSummary Depression during the postpartum (PPD) is of great concern based on its prevalence, especially in high risk groups of women. PPD has been associated with less optimal interactions with infants, including greater negativity and more disengagement of mothers. These qualities of interaction have been linked to adverse outcomes for the development and mental health of children. Thus, elucidating factors that heighten risk for problematic interactions is essential. The purpose of this study is to characterize the qualities of mother-infant interaction among women at high risk for PPD, determine the degree to which severity of mothers' depressive symptoms may be associated with these interactions, and test theory-based and empirically based moderators of the association between PPD and the quality of mother-infant interactions. These moderators include mental health problems that are common co-morbidities with a mother's depression (anxiety and substance abuse), her exposure to adversity (poverty, lack of family/partner support, and history of trauma), and the infant's gender, neonatal health, and temperament. We will also examine the role of infant development, by comparing differences in the strength of various relationships when the infant is 6 months versus 1 year of age. The study will capitalize on a rich foundation of existing datasets and video-records from 7 studies across 3 sites that, together, yield a sample size with the necessary power to examine multiple associations and test moderating effects. The sample includes 749 women who are at high risk for depression because of a previously diagnosed mood disorder, exposure to abuse, or the birth of a medically fragile infant. The initial 18 months of the study will involve ratings of mother- infant video-recorded interactions using the NICHD Mother-Infant Interaction Scales, merging of individual study data into a pooled REDCap database, and development of commensurate measures with common metrics across studies for all depression and moderating variables. Analysis and interpretation of pooled data to examine the research aims will occur in the final 6 months. The measurement model will employ varied methodologies, including standardized scores, factor analysis and item response analysis. Structural equation modeling will be used to examine the aims, while delineating and adjusting for sources of between-study heterogeneity. This research has the potential to 1) improve identification of mothers and infants whose interactions may be most vulnerable to the effects of PPD, and 2) enable the tailoring of interventions to reduce the infant's risk for later development of psychopathology that has been associated with having a depressed mother.